2Ó3 



of the calyx, between which are deep clefts extending inward between the centrodorsal and the 

 radials as in Zenometra and the large species of Psathy rometra. 

 This genus includes only the following species. 



i. Atopocriiuis sibogac A. H. Clark. 



A. H. CLARK. Notes from the Leyden Museum, vol. 34, p. 151. 



Stat. 177. 2°24'.5S., I29°38'.5E. Ceram Sea. 1633 Metres. 1 Ex. 



The centrodorsal is elongate conical, 5.5 mm. broad at the base and 7 mm. long, the 

 sides straight. Five strong interradial ridges each about as broad as the adjacent columns of 

 cirrus sockets divide the lateral surface of the centrodorsal into five radial areas each of which 

 is divided by a narrow median ridge which, except at the base, is as high as the interradial 

 ridges. The distal border of each cirrus socket is produced outward forming a strong ridge 

 across the proximal border of the one next below. Thus each cirrus socket occupies an 

 approximately oblong rather deep pit bounded proximally and distally 

 by these ridges just desenbed, and laterally by the longitudinal interradial 

 and radial ridgres. There are thirteen or fourteen cirrus sockets in each 

 radial area, making about sixty-eight in all. The youngest cirrus sockets, 

 on the proximal margin of the centrodorsal, project above the general 

 surface of the latter, appearing like the first segment of a cirrus. Each 

 cirrus socket bears on either side of the minute central canal (which is 

 slightly below its centre) a strong rounded (fulcral) ridge; this, like the 

 produced distal border of the cirrus sockets, gradually decreases in 

 height proximally, but much more rapidly decreases in height distally. 

 These transverse fulcral ridges are on either side produced outward to 

 a point which is somewhat higher than the general surface of the inter- 

 radial and the radial ridges between the columns of cirrus sockets, so 

 that in profile these ridges appear very strongly serrate, the radial rather 



more so than the interradial, the teeth of the serrations being convex proximally and concave 

 distally ; in a lateral view of the centrodorsal these projections appear as alternating bracket-like 

 processes proximally arising gradually but distally terminating abruptly in a straight horizontal 

 border. On the interradial ridges these projections are separated by a median free bare area 

 about equal to their own lateral height, but on the radial ridges they occur almost in a straight 

 line. As in Zenometra and in Psatkyrometra deep subradial clefts occur between the radials 

 and the centrodorsal; in height these are equal to one half of the dorsoventral diameter of the 

 topmost fully developed cirrus sockets. 



High and narrow basal rays, of which the outer ends are broadly pentagonal and 

 convex, cap the proximal ends of the interradial ridges and extend inward under the radial 

 pentagon, forming the sides and the blind inner wall of the subradial clefts. 



The cirri are lacking. 



The radials are about twice as broad as high in the median line, but recumbent, so 



Lateral view of the specimen 

 of Atopocrimis sibogae from Stat. 

 177. X 2 - (Courtesy of the l". S. 

 National Museum). 



